Electrical pulse generating apparatus



May 6; 1969 SEGALL, ET AL 3,443,152 ELECTRICAL PULSE GENERATINGAPPARATUS Filed April 10, 1967 INVENTORS Q t S LOUIS H. SEGALL BY IRVINGE. L|NKR 0UN m nevy United States Patent U.S. Cl. 315-209 11 ClaimsABSTRACT OF THE DISCLOSURE An electrical pulse generating system whereinuntimed pulses of two levels of energy may be selectively supplied to asingle load from a common source of electrical energy. The source isselectively connectable to different input terminals of two permanentlylinked condenser discharge circuits to selectively supply the sourceenepgy to one circuit or to divide the energy between the 'two' circuitsfor charging the storage condensers in said pircuits to preselectedlevels. One circuit is a power circuit for supplying pulses at one levelof energy to the load independently of the other circuit through acontrol gap; and the other circuit is a trigger circuit selectivelyadapted for energization simultaneously with the power circuit totrigger the control gap when the power circuit is charged to supply adifferent level of pulse energy to the1oad.

This invention relates to electrical apparatus and in particular to aspark generating system for providing at a common load terminal asuccession of voltage pulses at different selected energy levels from asingle energy supply source.

A principal object of the invention is to provide electrical apparatuscapable of selectively providing dual energy levels to a spark gapdischarge device for start and continuous operation of a combustionengine or the like.

Another object of the invention is to provide electrical apparatuscapable of selectively delivering two levels of energy to a storagedevice and controlling the discharge thereof through a spark gapdischarge device.

Another object of the invention is to provide electrical apparatushaving a control gap discharge device, including electrode meansexternal thereto for receiving high energy impulses to ionize the samefor conduction of different levels of stored energy.

Another object of the invention is to provide electrical apparatus forstart and continuous operation of a combustion engine at two energylevels, the components of said system, although being rated for thehigher energy level, are operated at low energy levels over considerabletime intervals, thereby subjecting the components to less stress andstrain to assure longer life of all components including the gapelectrodes and thus creating greater operating efliciency of the overallsystem with reduced maintenance costs and greater reliability over theextended time period.

A still further object of the invention is to provide in a dual energylevel ignition system for combustion engines electrical apparatus thatis simple, rugged, and efiicient.

The above and further objects and novel features of the presentinvention will more fully appear from the following detailed descriptionwhen the same is read in connection with the accompanying drawing. It isto be expressly understood, however, that the drawing is for the purposeof illustration only and is not intended as a definition of the limitsof the invention.

The single figure of the drawing is a diagram illustrating one form ofelectrical circuit embodying the invention.

3,443,152 Patented May 6, 1969 The embodiment of the inventionillustrated in the accompanying drawing is, by way of example, shown inthe form of a circuit for apparatus adapted for use as an untimedignition system in combustion engines or the like and so-called jet andgas turbine engines.

As shown in the drawing, one suitable embodiment of theminventioncomprises, as a source of electrical energy, an alternating currentgenerator .10 which may be connected to the remainder of the circuit bymeans of a single-pole, double-throw switch 11, interposed in the supplyleads 12 and 13, the input to the circuit under consideration. Eachinput lead has connected thereto suitable encased low pass filter means15, 16 for filtering out unwanted radio frequencies, noise frequenciesand the like, thereby preventing said extraneous frequencies fromfeeding back to the generator source and to other apparatus suppliedthereby. In the particular embodiment shown, the filter means comprisesby-pass condensers 17 connected between ground and each power supplyline, there being an inductance or choke coil interposed in each powersupply line between the by-pass condensers and the power source. Thepower supply lines beyond filters 15, 16 are designated 18 and 19.

The lines 18 and 19 are connected to the opposite ends 20 and 21,respectively, of an inductance coil 22. The coil 22 has connected acrossit a variable resistor 23 and transformer primary coil 24 of transformer25, the said resistor and transformer coil being series conne cted.Across transformer coil 24 there is connected a pair of diodes 26 and27, series connected, diode 26 being a silicon type rectifier and diode27 being a voltage regulator type Zener diode. The diode combination 26and 27 basically constitutes a voltage regulating circuit whereinone-half of the voltage wave input to transformer 25 is clipped. Thisassists in producing the proper timing of the trigger pulse over theignition system range of input voltage and frequency as embodied in theinvention herein.

The secondary coil 28 of transformer 25 drives a voltage diode rectifier29. The rectifier 29 has one terminal thereof connected to one extremityof transformer coil 28, the other rectifier terminal being connected toan electrode 30 of a control spark gap 31. The other electrode 32 of thespark gap 3.1 is grounded. Also connected to spark gap device 31 is atrigger condenser 33, one terminal thereof being connected to electrode30 and the other terminal to the primary coil 34 of pulse transformer35. The other extremity of primary coil 34 is grounded. The secondarycoil 36 of pulse transformer 35 also has one extremity thereof connectedbetween ground and primary winding 34 and the other extremity connectedto an external electrode 37 of a control spark gap device 38.

A relatively high voltage rectifier circuit connected to the same supplysource 10 is also provided and comprises a transformer 40 having one endof its primary winding 41 connected to terminal 21 of inductance coil 22and the other end grounded. The secondary winding 42 of transformer 40drives a voltage doubling circuit 43 comprising a diode 44 having oneterminal thereof connected to the one extremity 45 of coil winding 42and polarized in one direction, and another diode 46 having one terminalthereof connected to the same coil winding terminal 45, but polarizedoppositely to diode 44. A resistor 47 is connected between the otherterminal of diode 44 and ground. A pair of series connected capacitors49 and 50 are connected between the other terminal 51 of diode 46 andground, and the midpoint 52 of the series connected capacitors isconnected to the other extremity 53 of secondary coil 42 of transformer40. A condenser 57 is connected across primary coil 41 and a condenser58 is connected across coil 22 so as to reduce or attenuate radiofrequency interference which may be introduced into the ignition systemfrom other sources and produce faulty ignition or mis-firing.

The voltage doubling circuit may be constructed and may operate in themanner disclosed in Loudon US. Patent No. 3,299,339. When the voltagesupply is in one phase, only diode 46 conducts, and it will conduct inone direction only and thereby cause capacitor 49 to charge in onedirection. Upon phase reversal of the supply voltage, diode 44 aloneconducts, causing capacitor 50 to charge, the charge being of the samepolarity as that of the charge applied to capacitor 49. Since bothcapacitors are in series in their discharge circuit, their voltages willadd, thus doubling the source voltage.

The capacitor terminal 51 has connected thereto a resistor 59, theopposite end of the resistor being connected to a terminal 55 of astorage capacitor 54, the other terminal of the capacitor 54 beinggrounded. The ungrounded terminal 55 of capacitor 54 is connected to theother end of transformer coil 28. A high ohmic valued resistive element56 is connected across and in parallel with capacitor 54 to allowresidual leakage therefrom after the cyclical discharge of the saidcapacitor to be described.

Terminal 55 of capacitor 54 is connected to an electrode 60 of spark gap38 and has also connected thereto one terminal 61 of a capacitor 62, theother terminal of the capacitor '62 terminating in one of theextremities 63 of primary winding 64 forming part of a pulse transformer65. The other end 66 of primary winding 64 is connected to the otherelectrode 67 of the spark gap device 38. The secondary winding 68 oftransformer 65 has one extremity thereof also connected to spark gapterminal 67, the other extremity 69 of the said winding being connectedto a discharge gap device or igniter plug 70 which contains the usualspark gap 71 which may, but need not necessarily, be shunted by aresistance 72 which may be in the form of a semi-conductive surfaceacross the spark gap. The other side of the discharge gap device 70 isconnected to ground. A low ohmic valued resistance element 73 has oneterminal thereof connected to gap electrode 67 and the other extremitygrounded.

For high level energy excitation the source voltage is switched byswitch 11 to the input lead side 12 so as to place full line voltage,which may be on the order of 100 to 120 volts at 400 cycles, across thetransformer primary 41 of transformer 40. The voltage appearing acrosstransformer 25 is reduced substantially to zero because the primary coilis effectively shorted out. On the other hand, the full source potentialwill appear across transformer 40 and the voltage appearing acrossdischarge capacitor 54 will be relatively high.

The charging of condenser 54 to its peak voltage, as determined by thevoltage doubling circuit 43, will cause a similar charging of condenser62 to be effected. The charging of said condenser 62 will permit itsvoltage to appear across spark gap electrodes 60, 67 of spark gap 38,causing the gap to ionize and conduct. Upon conduction, condenser 62will discharge through the spark gap 38, thereby permitting the currentpassing through the coil '64 to induce a large voltage in secondary coil68. The large voltage across coil 68 will be applied across dischargegap 71, thereby causing the ionization and conduction thereof. Whendischarge gap 71 conducts, the storage condenser 54 will dischargetherethrough to cause the ignition spark necessary for combustion.

The above represents operation of the system for supplying high levelenergy at relatively high voltage, as for example when starting acombustion engine. For continuous operations as in the low level energymode, the power source 10 is switched over by switch 11 to input lead13. The full line power voltage now appears partly across inductor 22and the primary winding 41 of transformer 40 which is in seriestherewith. The voltage across coil 22 appears substantially across theprimary coil 24 of transformer 25, so that the said transformer will beenergized as opposed to substantially no energization in the previouslydescribed high level energy case. Also since transformer 40 now has lessvoltage applied thereto across its primary, it will be less heavilyenergized than in the previous high level energy mode. However, thecondenser 33 will be charged to a voltage determined by the voltagesappearing across secondary coil 28 and the voltage appearing acrosscondenser 54. Since these voltages are series adding, the combinedvoltages will appear across the said condenser 33. This same relativelyhigh voltage will accordingly also appear across spark gap 31, the saidrelatively high voltage being sufiicient to cause ionization andconduction of the spark gap 31. Upon conduction of the spark gap 31, thecondenser 33 will discharge therethrough and the resulting current flowwill pass through coil 34 of pulse transformer 35. A high voltage willbe induced in the secondary coil 36, this voltage appearing at electrode37 to cause the ionization of gap 38. The spark gap thereupon will breakdown and conduct.

The ionization and conduction of spark gap 38, in the foregoing manner,permits the discharge of capacitor 62 and the current flow resultingtherefrom to induce the high induced voltage across secondary coil 68and discharge gap 71 as mentioned previously in connection with the highenergy level operation. Discharge capacitor 54, having a relativelyreduced voltage because of the lower voltage appearing acrosstransformer 40, will nevertheless discharge through the spark gap 38 anddischarge gap 71 after the same are thus rendered conductive. It can beappreciated here that because the voltage appearing across the dischargecapacitor 54 is reduced over extended periods of time, i.e., duringcontinuous low level mode operation of the combustion engine, the lifeof the said capacitor will be considerably extended and the probabilityof its failure in operation considerably reduced. Hence, reliability andcost considerations are considerably enhanced.

The circuit as shown in FIG. 1 representing an exemplary embodiment ofthe invention may have the particular component parts thereof rated inthe following manner depending upon whether the circuit is operating atlow or high energy levels:

(1) Low level operation, capacitor 33 is typically rated at .03microfarad and 2.5 kv., will be charged to 2.5 kv. and capacitor 54,typically rated at 5.5 microfarads and 2 kv., will be charged to 1.0kv., the voltage, 2.5 kv. being sufficient to cause conduction of sparkgap 31, which is rated for breakdown purposes at 2.5 kv. Pulsetransformer 35 will develop a voltage across its secondary 36, whencapacitor 33 discharges, that is approximately 8.0 kv., enough whenapplied to electrode 37 to cause ionization and conduction of spark gap38. The gap 38 is rated at 2.0 kv., but because of ionization it willbreak down at a reduced voltage, or 1 kv.; this voltage appearing oncapacitor 54 as well as on capacitor 62 which is rated at 0.25microfarad and 2.5 kv.

(2) High level operation, capacitor 54 is charged to 2.0 kv. andcapacitor 62 is also charged to 2.0 kv., said voltage being sufficientto break down gap 38 which is rated for 2.0 kv.

Thus, it is seen that the ignition circuit provides two levels of energyoutput, one at 2 kv. and one at 1.0 kv., and that the output energylevel can be selected by switching the power input selector switch.

Although only one embodiment of the invention has been illustrated inthe accompanying drawing and described in the foregoing specification,it is to be expressly understood that the invention is not limitedthereto but that it may be embodied in other specifically definedcircuits. For example, other well known sources of pulsating oralternating current may be provided in lieu of the generator-transformercombination illustrated. Additionally, the various parts of the circuitmay be rearranged with respect to each other without appreciablyaffecting the operation of the circuit.

What is claimed is:

1. In electrical pulse generating apparatus a first condenser, adischarge circuit connected across said condenser comprising a firstcontrol gap having spaced main electrodes and a triggering electrode,means for charging said condenser to a voltage below the spark-overvoltage of said gap, and triggering means for ionizing said gap torender the same conductive to the charge on said condenser, saidlast-named means comprising a second condenser, a charging circuit forthe latter comprising in series therewith the secondary winding of apower transformer, said first condenser and the primary winding of atriggering transformer, a discharge circuit for said second condensercomprising a second control gap and said primary winding of thetriggering transformer, and a triggering circuit comprising thesecondary winding of the triggering transformer connected across saidtriggering electrode and a said main electrode, whereby the chargeattained by said second condenser is the sum of the charge on said firstcondenser plus the charge supplied by said secondary winding of thepower transformer.

2. Electrical apparatus as defined in claim 1 wherein the means forcharging said condensers comprises an alternating current power supply,the primary winding of said power transformer, a second powertransformer having a primary winding and a secondary winding in thecharging circuit for said first condenser, an inductace connected inseries with said last-named primary winding and means connecting theprimary winding of said first-named power transformer across saidinductance.

3. Electrical apparatus as defined in claim 2 comprising means forconnecting said power supply across the primary winding of the secondpower transformer, whereby to charge said first condenser to thespark-over voltage of said first control gap without energizing thetriggering means therefor.

4. Electrical apparatus as defined in claim 2 comprising means forconnecting said inductance in series with the primary winding of saidsecond power transformer across said power supply whereby saidcondensers are simultaneously charged.

5. Electrical apparatus as defined in claim 1 wherein the circuitparameters are such that said second condenser will be charged to thespark-over voltage of said second control gap before the charge on saidfirst condenser attains the spark-over voltage of said first controlgap.

6. Electrical apparatus as defined in claim 1 comprising a diode in saidcharging circuit for the second condenser.

7. Electrical apparatus as defined in claim 1 comprising rectifier meansin the charging circuit for said first condenser.

8. Electrical apparatus for producing low and high level energy outputsto a combustion engine comprising: an energy source, a first spark gaphaving an electrode thereof grounded, first condenser means connected tothe other spark gap electrode, stabilized voltage means driven by saidenergy source for charging the said first condenser to a firstpredetermined voltage level at the low level energy output, a secondspark gap including an external electrode connected thereto, secondcondenser means connected across said second gap, voltage amplificationmeans driven by said energy source for charging said second condensermeans to a second predetermined voltage level, storage condenser meansconnected to said second gap and ground for receiving a charging voltageequivalent to said second predetermined voltage, the said predeterminedvoltages being additive at the low level energy output across the saidfirst condenser means, first transformer means connected to said firstcondenser means and second gap external electrode, a discharge gaphaving an electrode thereof grounded, and second transformer meansconnected between said second spark gap and discharge gap.

9. Electrical apparatus for delivering separate energy levels to acombustion engine for start and continuous operation comprising a firstspark gap device, a second spark gap device, a first condenser connectedto said first device, a second condenser connected to said seconddevice, first and second voltage charging means for respectivelycharging said first and second condensers to preselected voltage levelsin accordance with start and continuous operation of the combustionengine, means interposed between said first and second gap devices andresponsive to the conduction of said first gap device during continuousoperation to produce high voltages at the said second gap device toeffect ionization and conduction thereof, and to allow the dischargetherethrough of the charge on said second condenser, and means forreceiving the discharge current of said second condenser at thepreselected levels for producing an ignition spark at the saidcombustion engine.

10. Electrical apparatus for producing low and high level energy outputsto a combustion engine comprising a first spark gap having an electrodethereof grounded, first condenser means connected to the other spark gapelectrode, a second spark gap including a triggering electrode connectedthereto, second condenser means connected to said second spark gap,means for selectively charging said first and second condenser means,the charging voltages therefore being additive across the firstcondenser means to cause conduction of the first spark gap for low levelenergy output, first transformer means connected to said first condensermeans and to the second gap triggering electrode, a discharge gap havingan electrode thereof grounded, and second transformer means connectedbetween said second spark gap and discharge gap.

11. Electrical apparatus according to claim 10 wherein said firsttransformer means includes a primary winding for receiving the dischargecurrent of said first condenser during low level energy output operationto cause a high secondary ionizing voltage to appear at the second gaptriggering electrode and thereby cause the conduction thereof.

References Cited UNITED STATES PATENTS 2,632,133 3/1953 MoNulty 315209 X2,910,622 10/1959 McNulty et al. 315-223 X 2,938,147 5/1960 Rose 315-4603,125,704 3/1964 Blackington et al. 3l5209 3,127,540 3/1964 Collins 3153,275,884 9/1966 Segall et al. 315163 FOREIGN PATENTS 929,070 6/1963Great Britain.

JOHN W. HUCKERT, Primary Examiner. R. F. POLISSACK, Assistant Examiner.

U.S. Cl. X.R. 315223, 239

